Studies of hereditary angioedema continue. Patients have been studied for signs of other related illness or drug toxicity. We now have over twenty patients with autoimmune disease and hereditary angioedema (granulomatous bowel disease, glomerulonephritis, thyroiditis, Grave's disease, and Rheumatoid Arthritis, etc.). A large subgroup have developed a disorder not thought to be autoimmune. These patients have ulcerations of the upper GI tract. Efforts are underway to purify the C1 inhibitor, to study its activity and to purify abnormal C1 inhibitor, to study its activity and to purify abnormal C1 inhibitor from a number of patients with acquired angioedema. Patients with PNH have been shown to have abnormally low numbers of B-FUE and C-FUE in their peripheral blood, explaining the aplastic state in these patients. Laboratory studies have emphasized complement receptors. These are cellular receptors important in phagocytosis. Peripheral blood monocytes have a C3b receptor and C3bi receptor but do not have a C3d receptor. We have found that on culture on glass or plastic the cells show rapid alteration in their surface receptors and develop a C3d receptor.